Assembly comprising an adjustable capacitor and a printed circuit

ABSTRACT

A capacitor, fixed to a printed circuit, comprises a ceramic stator with a continuous metallic layer extending partially over two sides thereof. One side of this layer forms the first plate of the capacitor and the other side is connected to a first part of the printed circuit. A metallic rotor member having a recessed surface is applied by elastic means against a dielectric layer adjacent said one side of the stator. The rotor is mounted on a conducting axle extending through the stator and terminating with a conducting collar protruding from the other side of the stator but not contacting the metallic layer. A connector element, for example either a further conducting layer on the other side of the stator or a spring, connects the collar to a second part of the printed circuit.

Field of Search ..3l7/249 R, 249 D, 101 C, 101 CP 0 H, a A: time Sttesatent [151 3,656,033 Niides et al. [45] Apr. H, 1972 [5 ASSEMBLYCOMPRISING AN f n s Cit d ADJUSTABLE CAPACITOR AND A FOREIGN PATENTS ORAPPLlCATlONS PRINTED CIRCUIT 807,382 1/1959 Great Britain "317/2490 [72]Inventors: Francois Nikles, Comaux; Henri T. Oguey,

peseux both of Switzerland 7 Primary Examiner-E. A. GoldbergAttorney-Stevens, Davis, Miller & Mosher I 73] Assignee: CentreElectronique Horloger SA,

7 Neuchatel, Switzerland I [57] ABSTRACT [22] Filed: Dec. 7, 1970 Acapacitor, fixed to a printed circuit, comprises a ceramic stator with acontinuous metallic layer extending partially over [21] A 95,634 twosides thereof. One side of this layer forms the first plate of thecapacitor and. the other side is connected to a first part of theprinted circuit. A metallic rotor member having a recessed I [30]Foreign Application Priority Data surface is applied by elastic meansagainst a dielectric layer I adjacent said one side of the stator. Therotor is mounted on a Dec. 17, 1969 Switzerland ..18730/69 conductingaxle extending through the stator and terminating with a conductingcollar protruding from the other side of the 101 C, 317/101 CP statorbut not contacting the metallic layer. A connector ele- [51] lnt.Cl...H0lg 5/06 ment, for example either a further conducting layer on the[58] other side of the stator or a spring, connects the collar to asecond part of the printed circuit.

i 7 Claims, 6 Drawing Fi I I Patented April 11, 1972 3,656,033

2 Sheets-Sheet 2 ASSELY comrnrsmo AN ADJUSTABLE CAPACITOR AND A 1 .1

BACKGROUND OF THE INVENTION The present invention concerns an assemblyof the type comprising an adjustable capacitor and a printed circuit, inwhich the capacitor comprises a ceramic stator carrying a first plateand having a dielectric layer adjacent the first plate, a rotor formedof a metallic member having a recessed surface adjacent the dielectriclayer, said rotor forming a second plate and being rotatably mounted ona conducting axle, and elastic means for axially urging the rotoragainst the stator.

SUMMARY OF THE INVENTION An object of the present invention is toprovide an assembly of the above mentioned type the thickness of whichcan be greatly reduced. Accordingly, the invention provides animprovement in an assembly of the above-mentioned type comprising acontinuous metallic layer extending at least partially over two parallelsurfaces of the ceramic stator, said metallic layer on a first surfaceof the stator forming said first plate, said metallic layer on a secondsurface of the stator contacting a first conducting part of the printedcircuit. The conducting axle of the rotor is fixed to a conductingcollar protruding from the second surface of the stator but notcontacting said metallic layer, and a connector element is arranged tobear against said collar and against a second conducting part of theprinted circuit.

This assembly can be used in various electronic circuits, and isspecially suitable when the dimensions of the assembly must be verysmall. It also enables reduction of the number of connections becausethe printed circuit is used as a contact.

DESIGNATION OF THE DRAWINGS The accompanying drawings show, by way ofexample, two embodiments of an assembly according to the invention, andvariants thereof. In the drawings:

FIG. 1 is a cross-section of a first embodiment;

FIG. 2 is a cross-section of a second embodiment;

FIGS. 3 and 4 are respectively an underneath plan view of a rotor, and across-section of the rotor; and

FIGS. 5 and 6 are underneath plan views of two variants of a rotor.

DESCRIPTION OF PREFERRED EMBODIMENTS The capacitor of the assembly shownin FIG. 1 comprises a ceramic material stator in the form of a disc 1provided with a layer 2 formed by the metallisation of a part of thesurfaces of the ceramics disc 1. This layer extends over parts of thetwo faces of the disc connected by a metallised coating over a part ofthe edge of the disc 1. The part of the layer 2 on the upper surface ofthe disc 1 forms a first plate of the capacitor. The part of the layer 2on the lower surface of the disc 1 terminates some distance away from acentral bore in the disc. All of the upper surface of the stator disc 1is covered by a dielectric layer 3, which is thin, of a high dielectriccoefficient, and is accurately planar so as to obtain a highcapacitance.

The rotor is formed by a metallic plate 21 which also has an accuratelyplanar lower surface, but having a hollow section 22, forming a secondplate of the capacitor. This surface rests on the upper surface of thedielectric layer 3 of the stator. The rotor plate 21 is, in thisexample, of polygonal shape so that it can be turned by means of asuitable tool.

The rotor plate 21 is rotatably mounted about a metallic axle 23 tightlyfitted in a metallic collar-piece 224, the collar of which bears againstthe lower surface of the ceramic disc 1. The upper end of the rotor axle23 has a head 25 projecting above the rotor plate 21. A leaf springacts, on the one hand, under this head 25 and, on the other hand,against the upper surface of the rotor plate 21. The axle 23 beingtightly fitted in the collar piece 24, the pressure of the leaf spring26 urges the rotor plate 21 against the dielectric layer 3 of thestator. Additionally, the collar of the piece 24 is pressed against thelower surface of the ceramic disc 1. This lower surface has a secondmetallised layer 27 insulated from the layer 2 and in contact with thecollar of the metallic piece 24. The part of the metallised layer 2situated on the lower surface of the ceramics disc 1 and the metallisedlayer 27, which are the terminals of the capacitor, are soldered ontoparts of a printed circuit applied on a surface of a support plate 20.

The part of the collar piece 24 extending beyond the lower surface ofthe stator is housed in an opening 28 of the support plate 20 for theprinted circuit, and within the thickness of this plate.

The capacitor of the assembly shown in FIG. 2 is mounted on a printedcircuit which is printed on both sides of a support plate 20. Thecapacitor comprises, as in the example of FIG. 1, a ceramic disc 1covered with a metallised layer 2 extending partially over the twosurfaces of the disc but connected by a metallisation on the interior ofa central bore in the disc 1. The stator is fixed on the support plate20 for the printed circuit and is covered on its upper surface by adielectric layer 3.

- The rotor is formed by a metallic plate 31 provided with a hollowsection 32 in its surface contacting the dielectric layer 3 The rotoraxle 33 has a truncoconical head 35 countersunk in the rotor plate 31.The axle 33 is tightly fitted in a metallic tube with a collar 34mounted without play in the plate 20 of the printed circuit. A leafspring 36 bears, on the one hand, against the collar 34 which is locatedunder the plate 20 and, on the other hand, against the lower surface ofthe plate 20 thus setting up a connection between lower metallised parts40 of the printed circuit. The pressure exerted by the leaf spring 36between the collar 34 and the plate 20 is transmitted to the rotor plate31 through the head 35 of the rotor axle 33. In this embodiment, theconnection of the capacitor is provided on the two sides of the printedcircuit plate 20. The part of the layer 2 of the stator adjacent theprinted circuit 20 is preferably soldered thereto, so as to avoid anyaccidental rotation thereof during adjustment of the capacitor byrotation of the rotor 31. v

In the two described constructions, the rotor is formed directly by ametallic plate mounted on a metallic axle which thus sets up aconnection between this second plate of the capacitor and the printedcircuit,

The shape of the hollow section of the rotor, as well as that of themetallic layer on the stator, enable a variation of capacitanceaccording to a desired mathematical relationship, whilst conserving acorrect seating of the rotor on the stator.

' The shapes of the hollows can thus be numerous.

In FIGS. 3 and 4 there is shown a rotor in the form of a disc 42, thehollow section 41 extending over a half of the surface of this disc. Theseating of the rotor is provided by a metallic pin 43 fixed in the halfof the disc including the hollow section 41 and protruding by an amountequal to the depth of the hollow. An insulating ring 44 separates thepin 43 from the metallic disc 42.

It would also be possible to replace this pin by a layer of plasticmaterial filling the hollow section 41.

In the variant of the rotor shown in FIG. 5, the hollow section 51extends over a semi-circular segment the outer radius of which is lessthan the outer radius of the disc 52 in a manner to provide a supportingcrown-like segment 53 around the semi-circular hollow segment 51. Inthis variant, the value of the capacitance is a linear function of theangle of the rotor in relation to the metallic layer on the adjacentsurface of the sta- 101'.

In the variant shown in FIG. 6, the rotor disc 62 has a recessed section61 extending to its periphery. This recessed section 61 is defined by anare 63 of a circle eccentric to the axle of the disc 62. This shape ofrecessed section 61 ensures a good seating of the rotor disc 62 and,additionally, gives a relatively large minimum capacitance C and alinear variation of the capacitance as a function of the angularposition of the rotor The mathematical relationship giving the variationof the curve as a function of the angular position of the rotor can bechosen in a manner to linearize a value depending upon the capacitancebut which is not proportional thereto. The frequency of oscillation of aquartz crystal connected in series with the capacitor can be quoted asan example.

When the rotor is disc like, as shown in FIGS. 3 to 6, means (not shown)could be provided in the thickness of the disc to enable it to be turnedby means of a suitable tool.

What is claimed is: t

1. In an assembly comprising an adjustable capacitor fixed to a printedcircuit, the capacitor comprising a ceramic stator carrying a firstplate and having a dielectric layer adjacent the first plate, a rotorformed of a metallic member having a recessed surface adjacent thedielectric layer, said rotor forming a second plate and being rotatablymounted on a conducting axle, and elastic means for axially urging therotor against the stator, the improvement comprising a continuousmetallic layer extending at least partially over two parallel surfacesof the ceramic stator, said metallic layer on a first surface of thestator forming said first plate, said metallic layer on a second surfaceof the stator contacting a first conducting part of the printed circuit,the conducting axle of the rotor being fixed to a conducting collarprotruding from the second surface of the stator but not contacting saidmetallic layer, and a connector element arranged to bear against saidcollar and against a second conducting part of the printed circuit.

2. Assembly according to claim 1, in which the conducting collar isformed by a metallic collar-piece tightly fitted on said plate, saidmetallic layer on the second surface of the stator contacting a firstpart of the printed circuit on the first surface of the support plate,and wherein a spring simultaneously forms said elastic means and saidconnector element, the conducting collar being formed by a metalliccollar-piece tightly fitted on said conducting axle, and the springconnecting a second part of the printed circuit on the second surface ofthe support plate with the collar-piece.

4. Assembly according to claim 3, in which an end of said conductingaxle is countersunk in the metallic member forming the rotor.

5. Assembly according to claim l, in which a metallic pin isinsulatingly fixed in an opening in said metallic rotor member at arecessed part of said surface, said pin protruding beyond the recessedpart of said surface by an amount equal to the height of the recess.

6. Assembly according to claim 1, in which the recessed part of thesurface of said rotor is filled with anelectrically insulating material.

7. Assembly according to claim 1, in which the rotor comprises means toenable rotation thereof about said axle.

1. In an assembly comprising an adjustable capacitor fixed to a printedcircuit, the capacitor comprising a ceramic stator carrying a firstplate and having a dielectric layer adjacent the first plate, a rotorformed of a metallic member having a recessed surface adjacent thedielectric layer, said rotor forming a second plate and being rotatablymounted on a conducting axle, and elastic means for axially urging therotor against the stator, the improvement comprising a continuousmetallic layer extending at least partially over two parallel surfacesof the ceramic stator, said metallic layer on a first surface of thestator forming said first plate, said metallic layer on a second surfaceof the stator contacting a first conducting part of the printed circuit,the conducting axle of the rotor being fixed to a conducting collarprotruding from the second surface of the stator but not contacting saidmetallic layer, and a connector element arranged to bear against saidcollar and against a second conducting part of the printed circuit. 2.Assembly according to claim 1, in which the conducting collar is formedby a metallic collar-piece tightly fitted on said conducting axle, saidconnector element being formed by a conducting layer on the secondsurface of the stator insulated from said metallic layer.
 3. Assemblyaccording to claim 1, wherein the printed circuit is printed on opposedfirst and second sides of a support plate, said metallic layer on thesecond surface of the stator contacting a first part of the printedcircuit on the first surface of the support plate, and wherein a springsimultaneously forms said elastic means and said connector element, theconducting collar being formed by a metallic collar-piece tightly fittedon said conducting axle, and the spring connecting a second part of theprinted circuit on the second surface of the support plate with thecollar-piece.
 4. Assembly according to claim 3, in which an end of saidconducting axle is countersunk in the metallic member forming the rotor.5. Assembly according to claim 1, in which a metallic pin isinsulatingly fixed in an opening in said metallic rotor member at arecessed part of said surface, said pin protruding beyond the recessedpart of said surface by an amount equal to the height of the recess. 6.Assembly according to claim 1, in which the recessed part of the surfaceof said rotor is filled with an electrically insulating material. 7.Assembly according to claim 1, in which the rotor comprises means toenable rotation thereof about said axle.